Sold Copyright of Paradise Lost

In April 1667, English poet John Milton signed an agreement with Samuel Simmons, a London publisher, by which he sold the copyright of Paradise Lost for five pounds, plus five pounds for the sale of each of three subsequent editions, an edition comprising 1,500 copies. Milton received a second five pounds in April 1669, making a grand total of 10 pounds to the author of England's greatest epic. After his death, Milton's widow Elizabeth sold all remaining rights for eight pounds to Simmons, who became perpetual copyright owner. It's hard to imagine someone selling something of such great value for so little